Apple maintains exclusive "ownership" of all lowercase four character codes for their software and APIs.

Examples:

'hook' - the application signature for iTunes (notice that it is an Apple product and is therefore lowercase)

'8BIM' - the application signature for Adobe Photoshop.

'shor' - the ../AEDesc type code for a 16bit signed integer, also known as typeSInt16, typeSMInt, or typeShortInteger

In Python, four character codes are passed around as four character str (primarily for introspection purposes). Some Python code will automatically interchange four character codes with str, unicode, int, or long but that will not be the general case until Python 2.4 at the earliest. ../bgen may output constants that look like FOUR_CHAR_CODE('shor'), however FOUR_CHAR_CODE is (currently) a no-op and just returns the input string unchanged.

In C, four character codes are interchangable with 32 bit integer types and will usually be defined in an enumerator: